21765673 has 4 divisors (see below), whose sum is σ = 21775108. Its totient is φ = 21756240.

The previous prime is 21765647. The next prime is 21765683. The reversal of 21765673 is 37656712.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 2782224 + 18983449 = 1668^2 + 4357^2 .

It is a cyclic number.

It is not a de Polignac number, because 21765673 - 2²¹ = 19668521 is a prime.

It is a super-2 number, since 2×21765673² = 947489042285858, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21765643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1315 + ... + 6727.

It is an arithmetic number, because the mean of its divisors is an integer number (5443777).

Almost surely, 2^21765673 is an apocalyptic number.

It is an amenable number.

21765673 is a deficient number, since it is larger than the sum of its proper divisors (9435).

21765673 is an equidigital number, since it uses as much as digits as its factorization.

21765673 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9434.

The product of its digits is 52920, while the sum is 37.

The square root of 21765673 is about 4665.3695459202. The cubic root of 21765673 is about 279.2055413401.

The spelling of 21765673 in words is "twenty-one million, seven hundred sixty-five thousand, six hundred seventy-three".